目的 由于镁合金的高比强度以及良好的电磁屏蔽等特性,广泛应用于汽车制造及航空航天等领域,但也存在易腐蚀的问题。通过固-液-气三相界面中粗糙度与表面能之间的协同作用,实现在镁合金表面构建超疏水层,从而提高材料的抗腐蚀性能。方法 从润湿模型入手,分析了粗糙度在三相复合界面中对接触角的影响。实验中通过引入皮秒激光在金属表面构建多级微纳结构,分析了激光刻蚀间距对AZ31B镁合金表面微纳结构构建的影响。表征采用SEM、三维轮廓来分析表面的物理结构变化,再通过EDS、XPS分析表面化学成分的改变,最后比较不同间距下的接触角大小。结果 适中的激光刻蚀间距有助于形成理想的微纳米结构,再结合硬脂酸作用可快速降低表面能,实现超疏水特性。其中,40 μm间距展现出最大的接触角,达到150.27°。较小间距（20 μm）会导致表面过于粗糙,而较大的间距（150 μm）则使表面显得过于光滑,这2种情况都会降低表面疏水性。电化学腐蚀实验证明,经过皮秒激光刻蚀并经过硬脂酸浸泡后的镁合金样品,其表面电荷转移过程最难发生,耐腐蚀性最强。结论 通过激光刻蚀和硬脂酸浸泡,采用适中的激光间距,可以形成多级微纳结构。这种结构使镁合金表面获得超疏水特性,从而提高镁合金材料的防腐性。
Abstract
Magnesium alloys, especially AZ31B, are widely used in the automotive, aerospace, and electronics industries due to their low density, high specific strength, and excellent electromagnetic shielding properties. However, their high chemical reactivity makes them highly susceptible to corrosion in humid or saline environments, significantly limiting their service life. Constructing superhydrophobic surfaces on magnesium alloys has emerged as an effective strategy to improve corrosion resistance by regulating surface roughness and surface energy at the solid-liquid-gas triple-phase interface, thereby isolating the material from corrosive media. This study proposes a synergistic surface modification approach that combines picosecond laser ablation with stearic acid chemical treatment to fabricate stable superhydrophobic layers on AZ31B magnesium alloy. This approach aims to enhance the alloy's corrosion resistance in harsh environments.
The primary objective of this research is to enhance the superhydrophobicity and corrosion resistance of AZ31B magnesium alloy surfaces by employing picosecond laser structuring followed by stearic acid modification. Initially, hierarchical micro/nanostructures are fabricated by picosecond laser ablation, with laser parameters such as power and scanning speed systematically adjusted to study their influence on the resulting surface morphology and wettability. In sub-optimal conditions concerning power and speed, the laser ablation spacing is varied between 20 μm and 150 μm to investigate its impact on surface topography and wettability. SEM and 3D profilometry analyses demonstrate that laser spacing is pivotal in micro/nanostructure formation. An optimal range of 40-100 μm facilitates the creation of desirable hierarchical structures, promoting the Cassie-Baxter wetting state by trapping air beneath water droplets and reducing solid-liquid contact. Notably, a spacing of 40 μm yields the best superhydrophobic performance with a maximum water contact angle of 150.07°. In contrast, a 20 μm spacing results in excessive surface roughness that compromises hydrophobicity, while a 150 μm spacing produces insufficient surface texture, thereby limiting air entrapment and reducing hydrophobic efficiency.
In addition, the laser-textured surfaces are chemically modified with stearic acid to reduce surface energy further and enhance hydrophobicity. The long hydrocarbon chains of stearic acid molecules are chemically adsorbed onto the surface of magnesium ions, forming a hydrophobic organic layer. EDS and XPS analyses confirm the successful attachment of stearic acid molecules. EDS results show increased carbon and oxygen contents and a corresponding decrease in magnesium content after modification. At the same time, XPS confirms the formation of magnesium stearate through chemical bonding between the carboxyl groups of stearic acid and surface magnesium ions. This chemical modification is vital in stabilizing the superhydrophobic surface by significantly reducing surface energy.
Electrochemical corrosion tests are performed on three samples: untreated, laser-treated only, and laser-treated, followed by stearic acid modification. The latter (Sample 2) exhibits the highest corrosion resistance, with a corrosion potential (Ecorr) of -1.428 4 V and a corrosion current density (Jcorr) of 5.952 8×10-5 A/cm², significantly outperforming the other samples. Due to the superhydrophobic surface, the enhanced corrosion resistance is attributed to the reduced interaction between the metal substrate and corrosive agents.
This study demonstrates that combining picosecond laser ablation and stearic acid modification effectively constructs a robust superhydrophobic structure on AZ31B magnesium alloy. The control of laser ablation spacing is critical for achieving ideal surface morphology that supports the Cassie-Baxter state. Meanwhile, stearic acid self-assembly contributes to long-term stability by reducing surface energy. Combining micro/nanostructure engineering and surface chemical modification has been identified as a promising solution for protecting magnesium alloys against corrosion in aggressive environments.
关键词
镁合金 /
激光刻蚀 /
润湿模型 /
微纳结构 /
超疏水
Key words
magnesium alloys /
laser ablation /
wetting model /
micro-nano structure /
superhydrophobicity
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基金
阳江市省科技创新专项资金项目（SDZX2023004）; 五金刀剪激光加工技术研究及阳江推广应用
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